“Hey, Uncle Sy, what’s quantum?”
“That’s a big question for a small person, Teena. Where’d you hear that word?”
“You and Mommy were talking and you said that something had to do with quantum mechanics. I know car mechanics work on cars so I want to know what the quantum mechanics work on.”
“That’s a fun question, Sweetie, because there actually is a kind of car called a Quantum. Not very many of them and they’re made in England so you don’t often see one here. But the quantum mechanics we were talking about is completely different. I’ll take it one word at a time, OK?”
<sigh> “OK, but let’s sit on the porch swing, I can tell this will take a while.”
“Oh, it’s not going to be that bad. You know what mechanisms are, right?”
“Um.. they’re not like people or animals and they’re not like my tablet thingie…. They’ve got gears and things.”
“Good enough. A big part of physics is thinking about how mechanisms work and that’s called ‘mechanics.’ There’s lots of different kinds of mechanisms. Each kind has a different kind of mechanics, like ‘celestial mechanics’ which is thinking about how stars and planets move, and ‘fluid mechanics’ which is thinking about how liquids and gases move. With me so far?”
“So quantum mechanics is thinking about how quantums move. But what’s a quantum?”
“Quantum isn’t a thing, it’s a set of rules that add up to be a theory. The first rule is, it only applies to things that are very, very small. That’s what the word ‘quantum’ has come to mean — the smallest possible amount of something. So quantum rules apply to quantum-sized things.”
“As small as my water bears?”
“Much smaller. Things that are as small compared to a water bear as a water bear egg is small compared to you. Things like molecules and atoms, and those are made of lots of parts that are even way smaller.”
“Ooo, that’s teeny. How do you even see them?”
“Well, you don’t. They’re far too small to see even with a microscope. It’s worse — if you did try to see an atom’s parts, any light you could shine on them would move them around so they’re not where they were when you started to look.”
“Then how do the quantum mechanics people learn about them?”
“Umm… Ah! See that flock of birds flying past?”
“Mommy says they’re starlings but I think they’re blackbirds.”
“Could be either or both, it’s hard to tell when they’re in the air like that. Sometimes the two kinds flock together. If it’s a flock of starlings, the flock is called a murmuration, which is one of my favorite words.”
“Oh, that’ll be one of my favorites now, too. Murmuration, mmmurmuration, mmmm. I love ‘M‘ words.”
“Anyway, can you see what direction any one bird is flying?”
“No, there’s too many and they go back and forth and it’s too confusing and I like the shapes the whole murmuration makes.”
“But can you point to the middle of it and see how the pattern moves?”
“It’s right the— ooo, look, it did a spiral!”
“Murmurations are sorta like the kind of thing the quantum mechanics people work with. They look at lots and lots of quantum-size things to see how the typical ones and the special ones behave. Then they try to work out what the behavior rules are. Sometimes the rules are really simple, like the rules the birds use.”
“Birds use rules? I thought they could fly wherever they wanted to.”
“Sometimes they do, but if they’re flying in a murmuration they definitely follow rules. Most of them. Most of the time. If I were one of those birds, I’d stay about the same distance from each of my neighbor birds, I’d usually fly in about the same direction as my neighbors are flying, and I’d also aim at about the middle of the flo— murmuration. Scientists have found that just those three rules account for most of how a murmuration behaves. Cool, huh?”
“Simple rules for bird brains, that’s funny!”
“But look at the beautiful shapes those simple rules make.”
~~ Rich Olcott
Hard Science Ain't Hard 